I have looked here many times but this is the first time I am posting.

We just had our final install of our windows. This is our second batch and with a new company because the original company did not offer a High Solar Heat Gain Window.

We wanted to match the other windows so we did a pocket install like the other windows. The original installer placed wood under the window to support it and get it up to the window sill height. This installer brought them in and just set them on the window sill. When I questioned it he stated that it is only required to have 1/2 inch of support and it would be fine. I did not want to tell him how to do his job but the more I think about it the more I think that this is not correct. These are large 8 foot 3 section slider windows and most of the weight is just hanging in air.

I also noticed that they did try to put blocks under the first window but the window was not even touching them. When I asked about this I was told that it was a nailer board. he later removed them after we talked about this and said it is not needed anyway. There were no screws from the window frame through these boards at all.

The windows work OK and look good. The installer has been working for this company (or so they say) for 15 years. He said all of his installs are like this and have never had a problem. I don't want to stir the pot but I am concerned that with this much weight hanging out there that the frame is going to sag and give me problems.

These windows are 3 section sliders (25%, 50%, 25%) so the two sections on the ends are partially over the sill but the large center section is cantilevered over the sill by a few inches. The window is 5 ft tall so that section (4 ft x 5 ft) of double pane glass is just hanging out there. That is the section I am concerned about.

foam is used prior to trim being re installed. i would not recommend drilling any holes especially into the window itelf. you would immediately void any warranty. keep in mind, if the window was measured tightly with a very small gap, foam would not work anyway as it would not stay in the gap. thats when full perimeter foam wrap that comes attatched to the window is a benefit.

If that's the case, ask the installer to come back, remove the bottom sill adapter or capping, whichever he used, and fill it with something(LOW EXPANSION FOAM OR BLOCKS) if it bothers you that much. I think it should be ok if you bought good quality windows but the most important thing to me is always how you feel.....so whether it's needed or not structurally doesn't matter it's all about making you comfortable with the final product. We don't want you shaking your head everytime you walk past the window.

The windows are Northstar made in Canada. The gap under the window is about 1 inch but it is packed with fiberglass insulation. Removing the trim to install the foam sounds like a good idea but it is a lot of work.

I have always heard that vinyl windows sag over time. I just don't want problems 5, 10 or 15 years down the road. You guys so far seem to think that this is not a concern. This is building my confidence. I don't want extra work for the installers if it is not needed but I don't want to deal with this at a later date if it is an issue.

These windows are 3 section sliders (25%, 50%, 25%) so the two sections on the ends are partially over the sill but the large center section is cantilevered over the sill by a few inches. The window is 5 ft tall so that section (4 ft x 5 ft) of double pane glass is just hanging out there. That is the section I am concerned about.

Thx again

On 3-lite sliders I have always fully supported the exterior of the sill with solid wood. A 75-100 pound sash cannot be supported by air. It WILL sag if not supported.

Window foam remains soft and pliable, I would not count on this as anything structural. If the window is out of square it should have some type of blocking as it would not be touching the backside of the sill across the whole window and would be relying on the screws in the vertical side of the window. I will also put screws in the head to prevent sagging and for more secure mounting. If you pull the windows apart you might as well do as WFU said.

If that's the case, ask the installer to come back, remove the bottom sill adapter or capping, whichever he used, and fill it with something(LOW EXPANSION FOAM OR BLOCKS) if it bothers you that much. I think it should be ok if you bought good quality windows but the most important thing to me is always how you feel.....so whether it's needed or not structurally doesn't matter it's all about making you comfortable with the final product. We don't want you shaking your head everytime you walk past the window.

I would block solid under both CMRs foam the rest and cut the sill adapter tight. In thirty years of installs no call backs on that method.thewindownerd....

Last edited by TheWindowNerd on Sun Apr 08, 2012 9:58 pm, edited 1 time in total.

If that's the case, ask the installer to come back, remove the bottom sill adapter or capping, whichever he used, and fill it with something(LOW EXPANSION FOAM OR BLOCKS) if it bothers you that much. I think it should be ok if you bought good quality windows but the most important thing to me is always how you feel.....so whether it's needed or not structurally doesn't matter it's all about making you comfortable with the final product. We don't want you shaking your head everytime you walk past the window.

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